Axial fan assembly

ABSTRACT

An axial fan assembly comprises a rotating shaft adapted to be actuated in rotation and axial fan assembly sections. Each assembly section has one rotor, the rotor including a hub rotatably engaged with the shaft and a plurality of blades radially extending from the hub; and one stator in proximity and downstream of each rotor. The stator includes an inner ring rotationally receiving the shaft. A plurality of vanes radially are connected the inner ring, such that a swirl of a flow of air produced by the rotor is reduced when the flow of air goes through the stator. An end-to-end configuration is provided between the axial fan assembly sections so as to increase a static pressure at the outlet of the axial fan assembly.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application claims priority on U.S. Provisional PatentApplication No. 60/601,615, filed on Aug. 16, 2004, by the presentapplicant.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to fan assemblies, particularly to axialexhaust fans.

2. Background Art

Exhaust systems usually comprise a number of elements causing resistanceto the airflow, such as dampers, filters, coils, etc. Exhaust fans(a.k.a., axial fans) thus need to be able to produce an airflow at agreat pressure in order to overcome such resistance. Because they areable to overcome a greater static pressure, centrifugal fans aretypically used as exhaust fans. However, centrifugal fans aresubstantially more expensive to manufacture than axial fans and takemore space.

SUMMARY OF INVENTION

It is therefore an aim of the present invention to provide an improvedaxial exhaust fan.

Therefore, in accordance with the present invention, there is providedan axial fan assembly comprising a rotating shaft adapted to be actuatedin rotation; at least a first and a second axial fan assembly section,each assembly section having: at least one rotor, the rotor including ahub rotatably engaged with the shaft and a plurality of blades radiallyextending from the hub; and one stator in proximity and downstream ofeach rotor, the stator including an inner ring rotationally receivingthe shaft, an outer ring concentric with the inner ring, and a pluralityof vanes radially connecting the inner ring and the outer ring, suchthat a swirl of a flow of air produced by the rotor is reduced when theflow of air goes through the stator; and an end-to-end configurationbetween the axial fan assembly sections so as to increase a staticpressure at the outlet of the axial fan assembly.

Further in accordance with the present invention, there is provided anaxial fan assembly comprising a rotating shaft; at least one rotor, therotor including a hub rotatably engaged with the shaft and a pluralityof blades radially extending from the hub; and one stator in proximityand downstream of each rotor, the stator including an inner ringrotationally receiving the shaft, an outer ring concentric with theinner ring, and a plurality of vanes radially connecting the inner ringand the outer ring, the vanes having a cross-section becomingprogressively more arcuately curved toward the outer ring, such that aswirl of a flow of air produced by the rotor is reduced when the flow ofair goes through the stator.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus generally described the nature of the invention, referencewill now be made to the accompanying drawings, showing by way ofillustration a preferred embodiment thereof and in which:

FIG. 1 is a longitudinal section view of an axial fan assembly inaccordance with an embodiment of the present invention, with a beltdrive;

FIG. 2 is an exploded view of the axial fan assembly of FIG. 1;

FIG. 3 is a plan view of a stator in accordance with another embodimentof the present invention;

FIG. 4 is a sectional view of the stator, taken along cross-sectionlines IV-IV of FIG. 3;

FIG. 5 is a longitudinal section view of an axial fan assembly inaccordance with another embodiment of the present invention, with a beltdrive;

FIG. 6 is an exploded view of the axial fan assembly of FIG. 5;

FIG. 7 is a plan view of a rotor of the axial fan assembly of FIG. 5;

FIG. 8 is a longitudinal sectional view of the rotor of FIG. 7 takenalong sectional line VIII-VIII of FIG. 7; and

FIG. 9 is an enlarged sectional view of an interconnection between a huband a blade of the rotor of FIG. 7, with a cover plate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIGS. 1 and 2, an axial fan assembly generallyindicated at 10 is composed of a plurality of stages 12 assembled in anend-to-end configuration. The fan assembly preferably includes at leasttwo or three stages 12 (i.e., axial fan assembly sections), as theembodiment illustrated herein does (three stages 12). Each stage 12 iscomposed of a rotor 14 located upstream of and adjacent to a stator 16.All rotors 14 and stators 16 are aligned, with a common rotating shaft18 passing through the center of each of the rotors 14 and stators 16. Adirection of flow of fluid through the axial fan assembly 10 isillustrated as A.

Each rotor 14 comprises a hub 30 which is rotationally engaged with theshaft 18. The hub 30 supports a plurality of radially extending blades32, so that rotation of the shaft 18 causes a rotation of the blades 32.Each blade 32 defines a leading edge 34, a trailing edge 36 and a bladetip 38. The blades 32 preferably have an appropriate airfoil profile, asis known in the art. The blades 32 also preferably have a twist.

Referring to FIGS. 3 and 4, each stator 16 comprises an inner ring 50 inwhich the shaft 18 is free to rotate, and may have an outer ring 52concentric with the inner ring 50, with the direction of flowillustrated as A. A plurality of vanes 54 extend between the inner ring50 and the outer ring 52 and are attached thereto. The vanes 54 eachhave a leading edge 56 and a trailing edge 58. The vanes 54 have a curve(as seen in FIG. 4) from the leading edge 56 to the trailing edge 58. Asbest seen in FIG. 1, the vane leading edges 56 are located in closeproximity to the blade trailing edges 36.

By adding more stages 12 (i.e., axial fan assembly sections) to the fan10 in the end-to-end configuration, the static pressure produced can beincreased without increasing the blade tip speed. Since, in a preferredembodiment, each stator 16 cancels the swirl of the airflow caused bythe preceding upstream rotor 14, increasing the number of stages willincrease the airflow pressure.

As best seen in FIG. 2, the fan assembly 10 has a pair of shells 60,which are assembled to enclose the rotors 14, stators 16 and the shaft18, thereby defining the tunnel of the axial fan assembly 10.

Moreover, the shells 60 define an enlarged intake 62 for the fanassembly 10. By the presence of a belt 64 for a belt drive, andassociated components such as the motor 66, the shaft pulley 68, and thecovers 70, some tunnel volume is lost, whereby the flaring shaft shapeof the enlarged intake 62 compensates for this loss of volume.

The shells 60 are also provided with access doors 72. The access doors72 facilitate access to an interior of the fan assembly 10, formaintenance. Accordingly, maintenance interventions, such as thereplacement of a bearing, is facilitated by the presence of access doors72.

It is also contemplated to provide each stage 12 with its own casingportion, such that an axial fan assembly 10 could be made up of modularend-to-end stages.

Such a configuration is advantageous in that the axial fan assembly 10is modular, whereby additional rotor 14/stator 16 assemblies may beadded to the axial fan assembly 10 for the assembly 10 to overcomegreater static pressures.

Although not illustrated, the axial fan assembly 10 may be actuated by amotor directly on the shaft 18, as an alternative to the belt drive.

Referring now to FIG. 5 to 9, an axial fan assembly in accordance withanother preferred embodiment is generally shown at 100 (FIG. 5). Aplurality of components are similar in both the axial fan assembly 10and the axial fan assembly 100, whereby like numerals will representlike components.

Referring to FIG. 5 to 9, a rotor used with the axial fan assembly 100is generally shown at 102. The rotor 102 of the preferred embodiment isused in a configuration similar to that illustrated in FIG. 1, in whicha sequence of rotors and stators are axially positioned in a cylindricalhousing so as to define an axial fan assembly.

For instance, the rotor 102 has a hub 104 by which the rotor 102 ismounted to the shaft 18 of the axial fan assembly 100 (FIG. 5), suchthat actuation of the shaft 18 will cause a rotation of the rotor 102about a longitudinal axis of the shaft.

The rotor 102 has a plurality of blades 106 projecting radially from thehub 104. It is best seen from FIGS. 6 and 7 that axial cover plates 108are provided on both sides of the rotor 102, in such a way that only aportion of the blades 106 extends beyond an outer periphery of the axialcover plates 108. This is also visible in FIG. 5, in which the axial fanassembly 100 shows only a portion of the blades 106, as a remainder ofthe blades 106 is hidden behind the axial cover plates 108.

The axial cover plates 108 are provided in order to increase the staticpressure of the axial fan assembly 100. More specifically, it is knownthat the tangential velocity of any point on any one of the blades 106increases from a center of the rotor 102 to a tip of the blades 106.Accordingly, the downstream pressure induced by the rotor 102 is greateropposite the tip of the blades 106 than opposite the center of the rotor102.

Considering that the pressure differential is nonnegligible, a back flowof air occurs near the center of the hub 104. The use of the axial coverplates 108 reduces the back flow passage area at the rotor 102, due tothe fact a central portion of the hub 104 is covered by the axial plates108. Therefore, the axial fan assembly 100 will produce a greater staticpressure with the cover plates 108 than without the cover plates 108.

Moreover, although two cover plates 108 are illustrated on the rotor102, it is contemplated to provide only one of the cover plates 108.However, the presence of a pair of cover plates 108 on the rotor 102will lessen any turbulence in the axial fan assembly 100.

Referring to FIGS. 8 and 9, it is illustrated how the blades 106 can beconnected to the hub 104 in view of the presence of the axial coverplates 108. More specifically, the blades 106 are shown having a bladeconnector 110. A securing ring 112 cooperates with the hub 104 to graspthe blade connectors 110, whereby the blades 106 are secured to the hub104. Fasteners 114 are used to connect the securing ring 112 to the hub104 with the blades 106 held therebetween. The axial cover plates 108are also retained to the hub 104 by way of the fasteners 114.

It is contemplated to use the rotor 102 with an associated stator, suchas the stator 120, in an axial fan assembly. However, to optimize theoperation of the axial fan assembly 100, cover plates similar to thoseillustrated at 108 in FIG. 6 can be provided for the stators used incombination with the rotors 102. Accordingly, an annular tunnel isdefined to facilitate air flow through the axial fan assembly 100.

Additional rotor/stator pairs can be added in a sequence similar to theaxial fan assembly 10 of FIG. 1, so as to increase the static pressureresulting from the operation of the axial fan assembly. The axial fanassembly of FIG. 5 is shown in a belt-drive configuration. Other typesof drives, such as a direct drive, can be used.

The embodiments of the invention described above are intended to beexemplary. Those skilled in the art will therefore appreciate that theforegoing description is illustrative only, and that variousalternatives and modifications can be devised without departing from thespirit of the present invention. Accordingly, the present is intended toembrace all such alternatives, modifications and variances which fallwithin the scope of the appended claims.

1. An axial fan assembly comprising: a rotating shaft adapted to beactuated in rotation; at least a first and a second axial fan assemblysection, each assembly section having: at least one rotor, the rotorincluding a hub rotatably engaged with the shaft and a plurality ofblades radially extending from the hub; and one stator in proximity anddownstream of each rotor, the stator including an inner ringrotationally receiving the shaft, and a plurality of vanes radiallyconnected to the inner ring, such that a swirl of a flow of air producedby the rotor is reduced when the flow of air goes through the stator;and an end-to-end configuration between the axial fan assembly sectionsso as to increase a static pressure at the outlet of the axial fanassembly.
 2. The axial fan assembly according to claim 1, wherein thevanes have a cross-section becoming progressively curved from a trailingedge to a leading edge.
 3. The axial fan assembly according to claim 1,wherein the fan assembly comprises at least three of the axial fanassembly section in the end-to-end configuration.
 4. The axial fanassembly according to claim 1, wherein the swirl is eliminated by thestator.
 5. The axial fan assembly according to claim 1, wherein therotor vanes are defined so as to have a curve.
 6. The axial fan assemblyaccording to claim 1, wherein each of the rotor has at least one coverplate covering a central portion of the rotor to reduce a back flowpassage area through the rotor.
 7. The axial fan assembly according toclaim 6, wherein each of the rotor has one of the cover plates on eachside thereof.
 8. The axial fan assembly according to claim 6, whereineach of the stator has at least one cover plate covering a centralportion of the stator, whereby a flow passage in the fan assembly has anannular cross-section.
 9. The axial fan assembly according to claim 8,wherein each of the rotor has one of the cover plates on each sidethereof.
 10. The axial fan assembly according to claim 6, wherein eachof the blades has a connector end so as to be connected to the hub ofthe rotor.
 11. The axial fan assembly according to claim 10, wherein theconnector end is retained between a securing ring and the hub.
 12. Thefan assembly according to claim 11, wherein a set of fasteners secureboth the securing ring and the cover plates to the hub.
 13. The axialfan assembly according to claim 1, wherein the axial fan assemblysections are enclosed in a tunnel consisting of a pair of longitudinalshells.
 14. The axial fan assembly according to claim 13, wherein anintake portion of the tunnel has a flared shape.
 15. The axial fanassembly according to claim 13, wherein at least one access door isprovided in any one of the longitudinal shells, to provide access to aninterior of the tunnel.